Electro-mechanical tuning of a c. w. magnetron



Nov. 26,1957 P- P. DERBY ETAI- 2,814,761

ELEcTo-MEQHANICAL TUNING oF A c.vg. MAGNETRON Filed June 7, l1955 United States Patent C) ELECTRO-MECHANICAL TUNING OF A C. W.

MAGNETRON Application June 7, 1955, Serial No. 513,917

4 Claims. (Cl. S15-39.59)

The present invention relates to a novel vand improved magnetron control apparatus and more particularly to novel .and improved :apparatus for controlling and/or modulating the frequency of a magnetron oscillator.

In the various types of conventional magnetron oscillators that are known in the art, it often becomes necessary and desirable to vary, control, and/or adjust the output frequency of the same. Althought many types of devices and Iapparatus have been devised in the past to mechanically tune and adjust the operating frequencies of such oscillators, considerable difliculty has been experienced heretofore in utilizing these devices to modulate the output frequency ofthe oscillators in accordance with a preselected relatively low frequency signal.

It is a principal object of the present invention to provide novel and improved modulation apparatus for an electron `discharge device.

It is a further object of the present invention to provide novel and improved modulation apparatus for an electronic magnetron which is relatively simple in construction and yet effective, reliable and stable in operation.

Other objects and many of the attendant advantages of this invention will be readily apprec-iated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein:

The figure is a cross sectional view of a preferred embodiment of the present invention.

In general the improved modulation apparatus of the present invention includes means defining a tuning cavity resonator external -to the magnetron, waveguide and gl-ass iris means for coupling the tuning cavity resonator to one of the resonant cavities in the anode block of the magnetron, a modulating signal source, and means responsive to the modulating signal source for varying the effect-ive area of the tuning cavity resonator in accordance with the frequency of the modulating signal source. It has been found that the amplitude of the output signal of the magnetron may be varied and/or modulated readily and reliably in this manner.

A preferred embodiment of the present invention is illustrated in the gure of the drawing. As shown therein, the tubular cathode 3 -of the magnetron circuit is coated with any suitable highly electron-emissive coating preferably of .the well known alkaline-earth metal oxide type. The heating filament 4 for the cathode which is energizedl by any suitable electrical source is preferably disposed as shown within the tubular cathode 3 so as to provide a ready supply of 'electrons for emission therefrom toward the concentric tubular anode block or the like 5. The cylindrical cavity resonators 6-11 in the block 5 are coupled to the electron discharge space between the anodeand cathode of the magnetron through their respective slots or the like 12-17. The outer yshell 18 of the m-agnetron is preferably arranged concentric with and dis` posed about the anode block as shown and includes the integral mounting flange or the like 18 on its upper surface.

ffice The transformer block or the like 19 is inset in the flanged surface of the anode block 5 such that the axial",

opening or slot 20 formed therein registers properly with the opening or passage 21 that extends upwardly from the cavity resonator 11 in the anode block 5. The glass window or iris 22 in the cap element or the like 23 which is secured 'over the upper extremity of the transformer block provides a vacuum seal for the interior of the magnetron and as will be more apparent hereinafter provides at the same time a high frequency connection between the internal cavity resonator 11 of the magnetron and its variable external chamber 24.

The annular member or disk 25 is arranged and adapted to fit atop of the flanged extremity of the anode' block 5 such that its upper surface extends a predetermined small 'amount above the upper surface of the transformer block 19. T-he .annular space or choke 26 between the flanged extremity of the anode block 5 and the annular disk 25 reects an infinite impedance for the energy within the chamber 24 above the transformer block 19 and in this way prevents loss 0f energy through that connection.

The cup shaped metallic yoke structure or the like 27 that `defines in part the chamber 24 is preferably secured to the upper surface of the annular disk 25 by means of the studs or the like 28. This yoke together with its end or cover plate 29, which is secured thereto by means of' the studs 30, forms the main magnetic path for the stepshaped permanent vmagnet 31 which is secured to the inner surface of the cover plate 29 by means of the stud 32 and extends downwardly therefrom through the `aper ture 33 in the base of the yoke 27.

The electric winding or coil 34 `is preferably disposed about the lower end of the magnet 31. -On'e extremity 35 of the coil is preferably grounded to the magnet yoke 27 at `any suitable point while the other extremity 36 of the' coil is connected to the terminal post -or the like 37 whiclr is mounted on the outer surface of the cover plate 29.

The cup-shaped reed element of the like 38 is positioned over the coil 34 and the magnet 31 and as will be more apparent hereinafter is adapted to change and con trol the effective area of the auxiliary chamber 24 between the counterbored portion 39 of the yoke 27 and the annular disk 25 as the axial position of the reed is varied.

The annular member 40 through which the -reed Iextends is secured in any suitable manner to the yoke prefer#y ably by means of the stud 41 land forms the cavity 42 between its lip portion 43 and the yoke. This cavity provides a high frequency choke for the energy in the chamber 24 and prevents its escape therefrom in the conventional manner. The flexible diaphragm -or the like 44 preferably extends between the upper peripheral surface of the :annular member 40 and the rim of the reed 38 to form an auxiliary seal for the device.

In operation after the natural frequency of the magnetron has become relatively stable that frequency may be readily varied and adjusted by changing the :axial position of the reed 38 fand therefore the eective area of the auxiliary resonating chamber 24. Changes of axial position of the reed land oscillations thereof are in turn produced and controlled readily by proper energization of the coil 34 in a manner similar to the energization and excitations of a conventional loud speaker assembly. Thus, when it is desired the natural frequency of the' magnetron may be conveniently modulated lby the fre` quency of the relatively low frequency source 45 which is: electrically connected to the coil 34 through the terminal post 37.

It is to be understood that the dimension-s of the various cavities and slots of the above described apparatus may be 'arranged and designed to function properly at any preselected natural frequency or group of frequencies without `departing from the spirit or scope of the present invention.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

Wh'at is claimed is:

1. Modulation yapparatus for an electron discharge device having a cathode and an anode which includes at least one resonant cavity said apparatus comprising a reed element; means including la peripheral portion of the reed element for dening a tuning cavity resonator outside of the anode; a transformer block positioned between the tuning cavity resonator and the resonant cavity, 4said` transformer block having a passage therethrough which electrically couples the tuning cavity resonator with the resonant cavity; a modulating signal source; an'd means responsive to the modulating signal source for controlling the position of the reed element with respect to the tuning cavity resonator.

2. Modulation apparatus for an electron discharge device having -a cathode and an 'anode which includes at leastone resonant cavity said apparatus comprising a reed element; means including a peripheral portion of the reed element for defining a tuning cavity resonator outlside of the anode; a transformer block positioned between the tuning cavity reson-ator and the resonant cavity, said transformer block having a passage therethrough which electrically couples the tuning cavity resonator with the resonant cavity; a modulating signal source; and means responsive to the modulating signal source for controlling the position of the reed element with respect to the tuning cavity resonator; a glass iris disposed between the transformer block and the tuning cavity resonator.

3. Modulation apparatus for an electron discharge device having ia cathode and Ian yanode which includes at least one resonant cavity said apparatus comprising a reed element; means including a peripheral portion of the reed element forv defining a tuning cavity resonator out-side of the anode; -a transformer block positioned between the tuning cavity resonator and the resonant cavity, said transformer block having a passage therethrough which electrically couples the tuning cavity resonator with the resonant cavity; a modulating signal source; and' means responsive to the modulating signal source for controlling the position of the reed element with respect to the tuning cavity resonator; a glass iris disposed between the transformer block and the tuning cavity resonator; electrical choke means which prevents the escape -of high frequency energy from the tuning cavity resonator.

4. Modulation apparatus for an electron discharge device having a cathode and an anode with a plurality of resonant cavities said apparatus comprising a magnetic circuit including a permanent magnet having an extremity that projects inwardly toward and defines Iin part the Kareal of va tuning cavity resonator; an electrical winding wrapped about the magnet; a cup shaped reed element .slidably positioned about the periphery of the winding; `a transformer block positioned between the tuning cavity resonator and one of the resonant cavities, said transformer block having a passage therethrough which electrically couples the tuning cavity resonator with the said one resonant cavity; a glass iris disposed between the transformer block and the tuning cavity resonator; electrical choke means which prevents the escape of high frequency energy from the tuning cavity resonator; a relatively low frequency source; and means responsive to energization of the low frequency source for energizing the magnet-ic circuit and for vibrating the reed element.

References Cited in the le of this patent UNITED STATES PATENTS 2,501,152 Becker Mar. 21, 195o 2,624,864 Herlin et al. Ian. 6, 1953 2,745,987 Dench May 15, 1956 

